1. Field of the Invention
The present invention relates to a probe for monitoring a fluid medium. More specifically, the invention relates to a probe including at least one fiber optic for emitting wave(s) into the fluid medium which scatters or causes luminescence of the emitted wave(s) which are then collected by at least one fiber optic.
2. Description of the Related Art
When an electromagnetic wave penetrates a fluid medium it may collide with one or more atoms. Some of the energy remaining after the collision will be transformed into scattering wave(s). In turn the scattering waves may produce other scattered waves. Various attempts have been made to collect such scattered waves after interaction with a fluid medium to monitor and analyze the fluid medium. In general, monitoring the fluid medium may include performing quantitative and qualitative analysis of elements, compounds and/or mixtures making up the fluid medium.
In addition, when an incident electromagnetic wave penetrates a fluid medium it may collide with one or more atom producing visible light a phenomena is referred to as luminescence. For example, when an electromagnetic wave collides with a phosphorous atom it may luminescence in the visible light range. Again the amount and type of luminescence reveals certain characteristics about the fluid medium.
The current state of probes has greatly limited the usefulness of Raman spectrometers to analyze fluid medium based on luminescence or scattered electromagnetic waves. One of the biggest limitations is low generation and collection efficiency of existing probes. For example, if a Raman spectrometer is to be used to analyze sparse Rayleigh photons, the probe must have larger acceptance angles or higher grazing fields than apparently are available.
FIG. 1 illustrates the limitations of a conventional fiber optic pair. To understand the problem consider that fiber optic 4 and 5 respectively emit and collect waves in cone-shape acceptance cones 31 and 32. Each acceptance cone 31 and 32 is bound by a divergent angle referred to as the numerical aperture which is defined by factors such as the type and size of the fiber optic core and cladding. A portion of the acceptance cones 31 and 32 will overlap at a volume 33 indicated by cross-hatching. Because the collecting fiber optic 5 can only collect that portion of the emitted waves in volume 33, the fiber optic pair of FIG. 1 will only collect reflected, scattered or Rayleigh waves within the limits of volume 33. This volume 33 is referred to as the "grazing field" and the larger the grazing field the higher the collection efficiency.
A conventional fiber optic typically has a numerical aperture of 10.degree.. Therefore, its grazing field will be quite limited and its collection efficiency low. Thus, conventional fiber optic pairs greatly limit the Raman spectrometers. Yet certain applications for this type of analysis exist in industry for real-time on-line monitoring of a fluid medium.
For example, in the polymer industry to monitor the temperature and pressure and composition of a polymer melt would be highly desirable. In other industries, involving chemical processing plants, oil refinery and distillation plants and smog and pollution detection, on-line monitoring of the pressure, temperature and composition of the fluid mediums is essential. However, apparently no existing probe can do such monitoring under these conditions. At best, the industry employs piezoresistive pressure transducers to monitor the high pressure and temperatures of polymer melts such as those described in U.S. Pat. Nos. 4,994,781 and 5,088,329 to Sahagen.
Such piezoresistive pressure transducers employ a pressure force collector diaphragm having one or more piezoresistive elements mounted thereon. The diaphragm with the piezoresistive elements is typically placed in a pressure cell base which maintains a low pressure or vacuum on one side of the diaphragm. External fluid medium under pressure contacts the other side of the diaphragm. A voltage is placed across the piezoresistive element(s) and as the diaphragm flexes in response to a pressure changes, a resistance change in the piezoresistive element(s) results in a change in the current flowing through the piezoresistive element(s).
Apparently, however, there is no on-line monitoring of the composition of polymers or other fluid medium at high temperatures and pressures. Thus, the composition of the polymer melts are not known on a real-time basis at high temperatures and pressures. The pressure and temperature of such polymer melts can reach up to 15,000 psi and to 800.degree. F. and above. In fact, in some polymer melt processes the pressure may go up to 1500.degree. F. or higher and the pressures up to 50,000 psi. Furthermore, in certain applications, the polymer melt will be a slurry viscous fluid having corrosive and abrasive properties which readily abrade and degrade conventional steel alloys and stainless steel posing additional obstacles to monitoring the polymer.
As a result, in the polymer industry, the polymer melt process is controlled by off-line sampling. The composition of the polymer melt is typically analyzed on a regular basis by extracting a sample of the polymer melt from the process for laboratory analysis. After analysis, a decision is made whether the polymer melt is suitable for production. Because such a laboratory analysis can require as much as four hours to perform off-line sampling can result in the production of considerable material not useful for its intended purpose. A large-scale polymer melt processing plant can generate in excess of $100,000 worth of polymer per hour. Thus, effective on-line monitoring of a high temperature and pressure polymer melt can result in large cost savings by preventing the waste of a large amount of material from which the polymer is derived on a monthly basis in one plant alone. Thus, a probe performing real-time on-line monitoring of not only the pressure and temperature, but also the composition of the polymer melt would be highly desirable. Accordingly, there is a great need in the polymer industry for a durable reliable probe which can monitor the high pressure, high temperature, composition and other physical properties of polymer melts.
In addition, there is a great need in the medical world for monitoring of blood, cancer, and abnormal cell growth within the body without the need for major surgery. For example, sometime surgery must be performed to determine the status or growth of cancer. When cancer is bombarded by certain electromagnetic waves, it will radiate scattered waves or luminescence waves which can be collected and analyzed. The characteristics of such waves will indicate the concentration, growth rate, and other important properties of the cancer. It would be highly desirable to have a probe which can use this phenomena to monitor cancer.
One technique for treatment of cancer in an internal organ involves irradiating the patient's body. Eradicating such cancerous growth can require irradiating both the affected organ and the surrounding tissue with high dosages of radiation. This is because the radiation must penetrate surrounding tissue, bodily fluids and perhaps other organs. This can have an adverse effect on the patient receiving the dosage, which in turn drastically limits the amount and corresponding effectiveness of the dosage.